1. Field of the Invention
The present invention relates to a cyan toner used in full-color copiers and printers to develop electrostatic images in electrophotography, electrostatic recording, electrostatic printing and the like, and a method of producing the cyan toner.
2. Related Background Art
Electrostatic printing, electrophotography and the like have been used as techniques to develop electrostatic latent images with a developer to form visible images. In these techniques, electrostatic latent images are formed on a photosensitive member, and developed with a toner to form toner images, which are then transferred to a transfer member such as paper, and heated, pressed, heated/pressed or exposed to solvent vapor, if it is necessary, to fix the images and thus produce duplicates. In the process, some of the toner is not transferred to the photosensitive member and cleaned off by any one of various cleaning methods to repeat the above process. In order to produce multicolor images, original color images are separated by color using color filters of B (blue), G (green) and R (red). Subsequently, the latent images composed of dots from 20 to 70 μm in size, which corresponds to the original images, are developed by color toners of Y (yellow), M (magenta), C (cyan) and B (black) which make subtractive color effects.
Recently, these image-forming devices have been used as office copiers as well as in the fields of printers as output devices for computers and personal copiers for individuals. In addition to such fields represented by printers, plain-paper fax machines with a basic image-forming engine incorporated therein have been developed to a great extent. Such trend has required strictly image-forming machines to be more compact, lighter, faster, more reliable and higher in image quality, and at the same time those machines have been simplified with respect to components in their various aspects. As a result, toners have been also required strongly to have a higher performance.
Especially, in full-color printers for personal computers and full-color copiers, such image-forming systems and toners have been sought as are well compatible with sRGB, which is the standard color space in this application field, and reproducible for a wider range of color, since a larger number of images from the Internet or personal computer displays have been outputted.
As a consequence, a colorant has been sought which is more transparent and more chromatic than C. I. Pigment Blue 15:3, a conventional colorant used for a cyan toner. Furthermore, a colorant used for a cyan toner has been required to be more reproducible in the blue color range as well as in the color ranges of cyan and green.
In order to accomplish these subjects, it has been proposed to use, as colorant, anthraquinone dyes/pigments (see Japanese Patent Application Laid-Open No. H07-043948), and zinc phthalocyanines (see Japanese Patent Application Laid-Open No. 2003-302792), triphenylmethane dyes/pigments (see Japanese Patent Application Laid-Open No. H02-073260) and indophenol dyes (see Japanese Patent Publication No. H06-027949). However, anthraquinone dyes, for instance, absorb light in a wavelength range from 400 to 500 nm, and thus they are so low in brightness as to be poorly reproducible in the color ranges of cyan and blue, though they are highly transparency. In contrast, zinc phthalocyanines behave well in the color ranges of cyan and blue, but their transparency is not adequate.